Machines such as, for example, passenger vehicles, trains, marine vessels, construction equipment, excavating machines, assembly line production equipment, etc., are often equipped with sensors for measuring operational parameters of the machine. These operational parameters may include, for example, engine RPM, oil pressure, water temperature, boost pressure, oil contamination, electric motor current, hydraulic pressure, system voltage, fuel consumption, payload, ground speed, transmission ratio, cycle time, and other parameters indicative of machine health, status, or performance. Storage devices may be provided on the machine to compile an operational parameters database or log for near real-time evaluation or for later evaluation of machine performance.
During operation, it may be beneficial to monitor the sensed operational parameters of a machine to diagnose and/or analyze its performance. As such, systems have been provided to monitor machine operational parameters and log faults, report events and parameter data points, and/or provide alerts in response to the monitored operational parameters. In some instances, the faults, events, and/or alerts may be communicated to one or more off-board systems responsible for tracking the operations of one or more machines (e.g., a fleet). For example, in response to oil pressure falling below a predetermined value and/or surpassing a predetermined contamination threshold, an oil change alert may be stored in a machine maintenance log, reported to the machine operator, and/or communicated to an off-board system.
In diagnosing an alert or malfunction, it is helpful to have data for some duration before the fault or event of interest occurred. However, the machine may have limited opportunity to communicate with the off-board system or may have limited bandwidth to communicate with the off-board system. The machine may also have a limited storage capacity, and may discard old data as new data becomes available. To increase the amount of useful data available while not having to increase memory on the machine or add bandwidth to the communications link, a method or system is needed to compress one or more parameter data points of one or more parameters.
One machine health monitoring system with data compression is described in U.S. Pat. No. 6,507,804 (the '804 patent) issued Jan. 14, 2003 to Hala et al. The '804 patent describes a method and apparatus for compressing, storing, and transmitting measurement data correlating to machine status. The method and apparatus sense the signal and extracts significant spectral elements, including magnitude and phase. Each set of spectral elements is compared to a previous set of spectral elements, and the new set is stored only if the sets vary by a user definable amount.
Although the machine monitoring system of the '804 patent may reduce the amount of memory required to store data, it has several shortcomings. For example, the method and apparatus of the '804 patent processes sensed signals, and not the parameter data points those signals represent. For instance, the method and apparatus of the '804 patent are designed for waveforms, such as rotational speed, and may not be suitable for a discrete value, such as a temperature or pressure. Additionally, the method and apparatus of the '804 patent are designed to process sensed signals rather than the products calculated from other parameter data points. For example, when a fan speed is calculated from the sensed pulse rate, the method and apparatus of the '804 patent may not reduce the memory space to store the calculated fan speed. A further drawback of the method and apparatus of the '804 patent is an inability to provide information on the predictability and variability of the compressed parameter data points, for example, by tracking the variance and mean square error of a linear progression of sensed parameter data points over time that are compressed into a single sensed parameter data point.
The disclosed system and method are directed to improvements in the existing technology.